An apparatus described in the Japanese Patent Application Publication No. 2005-75572 ejects sheets conveyed from an image forming apparatus onto a stacking tray. The stacking tray is mounted to a apparatus main body so as that the downstream side of the stacking tray in the sheet conveying direction is located higher than the upstream side of the stacking tray. Thereby, the sheet ejected on the stacking tray slides down on the slope of the stacking tray, and then the posterior end of the sheet hits a wall (or a grating) of the apparatus main body. The apparatus main body has a sensor for detecting the top of the stacked sheets on the stacking tray. The stacking tray moves up and down along the apparatus main body to a position where the sheets stacked on the stacking tray avoids blocking a sheet ejecting vent of the apparatus main body, based on a detection signal detected by the sensor.
However, in the above-mentioned device, when the stacking tray moves up and down in a state that the posterior end of sheets keeps contact with the wall surface of the apparatus main body, a noise occurs due to vibration of the posterior end of the sheets according to friction of the posterior ends of the sheets and the wall surface of the apparatus main body. In particular, in an overload state of the sheets or in a state that the sheets are thick, there is a problem that the noise according to vibration becomes large and yields troublesome for a user.
As a device having solved the above-mentioned problem, there is a sheet loading apparatus as disclosed in Japanese Patent Application Publication No. 2008-94612. This sheet loading apparatus is provided with a sheet receiving tray elevating in loading a bundle of sheets ejected from a sheet post-processing apparatus, a first driving source and an end-fence for aligning the posterior ends of the bundle of sheets. This end-fence is characterized by elevating in accompany with the elevation of a sheet receiving tray. Thereby, a disorder of the stack state caused by the posterior ends of the sheets rubbing against the end-fence, dirt or dent of the sheets, a noise caused by rubbing of the sheets against the end-fence.
In the above-mentioned sheet loading apparatus having a waiting tray and a processing tray, when there is no problem. However, there is a problem that, when sheets are ejected directly from the waiting tray to the sheet receiving tray, sheets unexpectedly enters into the opening portion of a processing tray.